External counterpulsation (ECP) is a noninvasive treatment for congestive heart failure, stable and unstable angina pectoris, acute myocardial infarction, cardiogenic shock and other cardiac disease. External counterpulsation refers to the method of squeezing a patient's lower body in syncopation with the patient's heart beat (that is, the lower body is squeezed between each heart beat). To accomplish this, a series of compressive air cuffs are wrapped around each leg; one at calf level, another slightly above the knee and the third on the thigh, and perhaps a cuff over the buttocks. A computerized control system interprets the patient's ECG, and operates valves and an air supply to inflate and deflate the bladders in synchronization with the R-wave of the patient's cardiac cycle. The R-wave represents the start of the diastole, which is the period during which the chambers of the heart expand and fill with blood. During diastole, the air cuffs are inflated sequentially (from the distal bladder on the calves to the proximal bladders on the upper thighs or buttocks), compressing the calves, lower thighs and upper thighs, and all the muscles and blood vessels of the leg. This squeezing action results in an increase in diastolic pressure, generation of retrograde arterial blood flow and an increase in venous return. The cuffs are deflated simultaneously just prior to systole, which produces a rapid drop in vascular resistance to blood flow, a decrease in ventricular workload and an increase in cardiac output.
When used to treat the chronic condition of congestive heart failure, many treatment sessions, spread out over several weeks, are used. A full course of therapy usually consists of 35 one-hour treatments, which may be offered once or twice daily, usually 5 days per week. In the short term, this method of therapy is thought to deliver more oxygen to the ischemic myocardium by increasing coronary blood flow during diastole, while at the same time reducing the demand for oxygen by diminishing the work requirements of the heart. Long-term benefit has been established by numerous studies. While researcher are still trying to determine why the therapy works, research has indicated that the therapy leads to increased coronary collateral flow to ischemic regions of the heart (though the mechanism leading to the effect is unknown). Clinical trials have demonstrated that the beneficial effects of ECP, including increased exercise time until onset of ischemia and a reduction in the number and severity of anginal episodes. These effects are not only sustained between treatments, but may persist for several months or years after the entire course of therapy.
The effectiveness of ECP treatment for chronic conditions is determined by the changes in diastolic pressure, systolic pressure, heart rate observed over the course of treatment. Currently, doctors and clinicians administering ECP to patients review a few strips of ECG and blood pressure data to determine if ECP performed on a particular patient is being performed properly and having a beneficial effect on the patient. Indications of beneficial effect include increased cardiac output, and, depending on the particular cause or manifestation of angina pectoris and/or congestive heart failure improved ECG, lower diastolic blood pressure, and a lower heart rate. Currently, a few paper strips which the operator collects during each session are collected in the patients chart for comparison of cardiac parameters during each session. No other data is collected, because it is not currently used. There is no generally accepted endpoint for the therapy, and no generally accepted method for determining if further therapy would be useful for a particular patient. Hence, the industry has settled on an apparently arbitrary 35 hour course of therapy. The treatment is offered on the basis that the patient will respond to therapy, and that 35 sessions will be sufficient. If a patient is well treated with 35 sessions, all is well and good for that patient. If, however, the patient would benefit from a longer course of treatment, none will be provided because there is no method of identifying these patients. If the patient would have been well treated with substantially less than 35 sessions, the complete 35 session therapy would then be considered to include a substantial amount of unnecessary treatment. The current absence of any mechanism for tracking and analysis makes it impossible to objectively determine if further treatment would be warranted.